RUBBERS AND GUMS 806 



GUTTA-PERCHA 



Gutta-percha is a product closely resembling true rubber 

 in chemical composition but differing from it decidedly in 

 physical properties. It is the product of a tree known as 

 Palaquium gutta and of several other species of more or less 

 related trees. These trees are native of Malaya, Cochin China, 

 Central America, South America, Australia, and the Philip- 

 pines. They are large trees of the family Sapotaceae, with 

 shiny leathery leaves, somewhat resembling those of certain 

 species of rubber trees. In harvesting the gutta-percha the 

 trees are cut down, after which the bark is removed and the 

 latex collected by mechanical and chemical methods, or the 

 trees are tapped by ringing or other kinds of incisions. The 

 leaves also yield about lo per cent, of a low grade of gutta- 

 percha which may be extracted with toluene. The gutta- 

 percha is collected in blocks or irregular lumps weighing s 

 to lo pounds. This mass is then put through a mangier, 

 washed, and rolled into sheets. Gutta-percha is readily soluble 

 in chloroform. It melts at moderate temperatures and is in- 

 elastic, differing in that respect from rubber. It is used in 

 surgical bandages, wound coverings, like collodion, and golf 

 balls, but chiefly for outside insulation of submarine cables. 

 For this purpose it has long been used in large quantities. 

 Gutta-percha has furnished a basis for the insulation of 250,- 

 000 miles of submarine cables. At present rubber is displacing 

 gutta-percha for most purposes, but the United States imported 

 1,900,000 pounds in 1914. Certain species of Sapota, Calo- 

 tropis, and Euphorbia also yield gutta-percha. Gutta-percha 

 is pliable at ordinary temperatures. It yields to pressure at 

 122° F., may be kneaded at 194° F., and melts at 248° F. It 

 is decidedly resistant to hydrofluoric acid and may therefore 

 be used in vats for etching glass. 



